Nowadays, LED backlights, digital displays, and lighting devices are usually obtained by packaging fluorescence materials. There are many patents for such devices, e.g., Chinese patent 200510030192.1 (“White luminous component and preparation thereof”), Chinese patent 200310120736 (“Surface mounting type white LED”), Chinese patent 200710151099.5 (“Blue-purple or blue light excitation phosphor and preparation method thereof, and packaged white LED”). Such patents all relate to white luminous devices prepared by mixing fluorescent materials with a resin and applying the mixture on a LED chip. The white luminous devices prepared by such methods are difficult to ensure consistent lightness, color coordinate, color temperature and color rendering properties. Moreover, the fluorescent powder is disposed close to the chip, and is prone to be aged due to heat, and thus has reduced life time.
WO2007105853 discloses a method for preparing a photoluminescent film, wherein the used luminescent material is an inorganic luminescent material. This patent only describes that the photoluminescent film is prepared with silicon resin as film-forming material, but does not describe the relationship between the luminescent material in the photoluminescent film and color coordinate, color temperature and lightness; moreover, the method does not use cast molding, and cannot form various shapes. WO2007/049187 describes an encapsulant film containing a phosphor blended with silicone; this film material is installed on a blue LED to convert blue light into white light. However, this material is in film-shaped structure, thus it needs post-forming by lamination according to service conditions, thereby the process is complex. US2008/0280957 A1 discloses a method for producing LED using a plastic device with lens structure, the bottom of the plastic device with lens structure is a structure comprising fluorescent material layer, and is prepared by die casting or injection molding. Therefore, the structure and process are relatively complex, and the shape cannot be changed after molding. Chinese patent 200810067358.0 (“A LED illuminating apparatus with low attenuation and high light efficiency and its preparation method”) and Chinese patent CN1858920A (“Packaging method for white LED lamp”) relate to a method for manufacturing transparent case by adding a fluorescent material into a polymer material and molding. This method is suitable for packaging single LED. The shape of the molded material cannot be changed, and thus its installation and application are restricted. Chinese patent CN101012916A (“A lamp using LED as light source”) discloses a method for fixing light converting material on the case of a lamp. Although this method avoids the problem of fluorescent material aging at high temperature, the material has a certain distance from the light source, leading to reduced luminescent efficiency of the fluorescent material. This method is only suitable for preparing products such as lamps or the like, and therefore has restricted application.